The steps to unbind a mobile phone number from a Temu sub-account are as follows:

1. Open and log in to the Temu merchant backend page, and then click the "Account Settings" menu.

2. After entering the "Account Settings" page, find the "Sub-Account Management" column and click to enter the sub-account management page.

3. On the sub-account management page, find the sub-account whose mobile phone number needs to be unbound, and then click the "Unbind Current Device" button below it.

4. On the unbinding page that pops up, after confirming that everything is correct, click the "Confirm Unbinding" button to complete the unbinding operation.

Please note that to unbind a mobile phone number, you need to first confirm that the mobile phone number is not used to receive and ship goods or log in to the order page, and that the mobile phone number has completed real-name authentication. If you encounter any problems during the unbinding process, you can contact Temu customer service to resolve it.